Rotary cutting tool having adjacent cutting inserts with wave-shaped edges and overlapping rotational trajectories coinciding in phase

Abstract

A rotary cutting tool has a plurality of circumferentially spaced grooves, each having a plurality of cutting inserts mounted. Each cutting insert has a wave-shaped major cutting edge, a corner cutting edge, and a minor cutting edge. The cutting inserts are arranged such that, the phases of the waves of the rotational trajectories formed by the cutting inserts that are adjacent to each other in a direction along the tool rotational axis coincide with each other in one groove. Also, the rotational trajectories of at least part of cutting edge portions of at least some cutting inserts are overlapped with each other in the direction of the tool rotational axis. Accordingly, even when the cutting edge portion is used as a major cutting edge and as an inner cutting edge, it is still possible to reduce cutting load and suppress breakage.

What is claimed is: 
     
       1. An indexable rotary cutting tool comprising: a substantially cylindrical tool body having a rotational axis; and cutting inserts mounted on the tool body, in which a plurality of grooves is formed in a peripheral surface of the tool body, a plurality of insert seats is formed in the grooves, and the cutting inserts are removably arranged onto the insert seats, wherein:
 the cutting inserts each have a rake surface and a flank intersecting with the rake surface, and a major cutting edge, a corner cutting edge connected to the major cutting edge, and a minor cutting edge connected to the corner cutting edge, are formed in an intersecting edge between the rake surface and the flank; 
 the major cutting edge has a wave shape formed of alternately connecting outwardly-curved cutting edge portions and inwardly-curved cutting edge portions of the major cutting edge as viewed from a direction facing the rake surface; 
 the cutting inserts are arranged:
 such that, in rotational trajectories formed by the major cutting edges of the respective cutting inserts when the indexable rotary cutting tool is rotated around the rotational axis, phases of waves of rotational trajectories formed by cutting inserts that are adjacent to each other in a direction along the rotational axis in one groove coincide with each other, and 
 such that at least some of the cutting inserts are arranged such that, from among the rotational trajectories formed by the major cutting edges, rotational trajectories formed by part of cutting edge portions are overlapped with each other in a direction of the rotational axis; and 
 
 in each of the grooves, the at least some cutting inserts are arranged such that, from among the rotational trajectories formed by the major cutting edges, only rotational trajectories formed by outwardly-curved cutting edge portions located closest to ends of the major cutting edges are overlapped with each other in the direction of the rotational axis. 
 
     
     
       2. The indexable rotary cutting tool according to  claim 1 , wherein, in all the grooves, all adjacent cutting inserts are arranged such that the rotational trajectories of ends of the adjacent cutting inserts are overlapped with each other in the direction of the rotational axis. 
     
     
       3. The indexable rotary cutting tool according to  claim 1 , wherein, in a relationship between the rotational trajectories of the cutting inserts arranged in grooves that are adjacent to each other in a circumferential direction of the tool body, the cutting inserts are arranged such that the phases of the waves of the rotational trajectories are shifted from each other in the direction of the rotational axis, and when the rotational trajectories of all the grooves are superimposed, the phases of the waves of the rotational trajectories of the grooves do not coincide with each other. 
     
     
       4. An indexable rotary cutting tool comprising: a substantially cylindrical tool body having a rotational axis; and cutting inserts mounted on the tool body, in which a plurality of grooves is formed in a peripheral surface of the tool body, a plurality of insert seats is formed in the grooves, and the cutting inserts are removably arranged onto the insert seats, wherein:
 the cutting inserts each have a rake surface and a flank intersecting with the rake surface, and a major cutting edge, a corner cutting edge connected to the major cutting edge, and a minor cutting edge connected to the corner cutting edge, are formed in an intersecting edge between the rake surface and the flank; 
 the major cutting edge has a wave shape formed of alternately connecting outwardly-curved cutting edge portions and inwardly-curved cutting edge portions of the major cutting edge as viewed from a direction facing the rake surface; 
 the cutting inserts are arranged:
 such that, in rotational trajectories formed by the major cutting edges of the respective cutting inserts when the indexable rotary cutting tool is rotated around the rotational axis, phases of waves of rotational trajectories formed by cutting inserts that are adjacent to each other in a direction along the rotational axis in one groove coincide with each other, and 
 such that at least some of the cutting inserts are arranged such that, from among the rotational trajectories formed by the major cutting edges, rotational trajectories formed by part of cutting edge portions are overlapped with each other in a direction of the rotational axis; 
 
 the minor cutting edge of the cutting insert is connected to a another major cutting edge different from said major cutting edge; 
 lands are formed in all of the major cutting edge the minor cutting edge, and the corner cutting edge; 
 a land width at a connecting point between said different major cutting edge and the minor cutting edge is larger than a land width at a center point in the different major cutting edge; and 
 a land angle at the connecting point between the different major cutting edge and the minor cutting edge is smaller than a land angle at the center point in the different major cutting edge. 
 
     
     
       5. The indexable rotary cutting tool according to  claim 4 , wherein a land width and a land angle of the minor cutting edge are equal to the land width and the land angle at the connecting point. 
     
     
       6. An indexable rotary cutting tool comprising: a substantially cylindrical tool body having a rotational axis; and cutting inserts mounted on the tool body, in which a plurality of grooves is formed in a peripheral surface of the tool body, a plurality of insert seats is formed in the grooves, and the cutting inserts are removably arranged onto the insert seats, wherein:
 the cutting inserts each have a rake surface and a flank intersecting with the rake surface, and a major cutting edge, a corner cutting edge connected to the major cutting edge, and a minor cutting edge connected to the corner cutting edge, are formed in an intersecting edge between the rake surface and the flank; 
 the major cutting edge has a wave shape formed of alternately connecting outwardly-curved cutting edge portions and inwardly-curved cutting edge portions of the major cutting edge as viewed from a direction facing the rake surface; 
 the cutting inserts are arranged:
 such that, in rotational trajectories formed by the major cutting edges of the respective cutting inserts when the indexable rotary cutting tool is rotated around the rotational axis, phases of waves of rotational trajectories formed by cutting inserts that are adjacent to each other in a direction along the rotational axis in one groove coincide with each other, and 
 such that at least some of the cutting inserts are arranged such that, from among the rotational trajectories formed by the major cutting edges, rotational trajectories formed by part of cutting edge portions are overlapped with each other in a direction of the rotational axis; and 
 
 the cutting inserts have a substantially triangular shape as viewed from a direction facing the rake surface. 
 
     
     
       7. The indexable rotary cutting tool according to  claim 6 , wherein:
 the major cutting edge is formed along each side of the substantially triangular shape of the cutting insert; and 
 in the plurality of outwardly-curved cutting edge portions, an outwardly-curved cutting edge portion located at an end of the major cutting edge and connected to the minor cutting edge also serves as an inner cutting edge. 
 
     
     
       8. An indexable rotary cutting tool comprising:
 a substantially cylindrical tool body having a rotational axis, a trailing end surface, a leading end surface and a peripheral surface; 
 a plurality of circumferentially spaced-apart grooves formed in the peripheral surface, each groove comprising a plurality of insert seats; 
 an indexable cutting insert removeably attached in each insert seat, each cutting insert having rake surface, an attachment hole formed in the rake surface around which the insert is indexable, and a plurality of sets of cutting edges, each set comprising a major cutting edge, a corner cutting edge connected to the major cutting edge, and a minor cutting edge connected to the corner cutting edge; wherein: 
 each major cutting edge comprises a plurality of spaced apart outwardly-curved cutting edge portions that are curved like arcs toward the outside of the cutting insert, in a top view of the cutting insert facing the rake surface and the attachment hole; 
 each cutting insert is attached such that an operative major cutting edge has a leading outwardly-curved cutting edge portion and a trailing outwardly-curved cutting edge portion; 
 in each groove, adjacent inserts are mounted such that a rotational trajectory of an outwardly-curved cutting edge portion at the trailing end of the leading insert coincides in phase with a rotational trajectory of an outwardly-curved cutting edge portion at the leading end of the trailing insert; and 
 in adjacent grooves, the cutting inserts located closest to the distal ends of the adjacent grooves are arranged such that rotational trajectories of the inserts' leading outwardly-curved cutting edge portions do not coincide in phase. 
 
     
     
       9. The indexable rotary cutting tool according to  claim 8 , wherein:
 each cutting insert has a substantially triangular shape as viewed from a direction facing the rake surface; 
 each cutting insert has three sets of cutting edges, one set of which is operative and has a major cutting edge extending along the peripheral side surface; and 
 the major cutting edge of each set is formed along a corresponding side of the substantially triangular shape. 
 
     
     
       10. The indexable rotary cutting tool according to  claim 9 , wherein:
 each groove has a plurality of cutting inserts seating therein, and rotational trajectories of overlapping outwardly-curved cutting edge portion belonging to adjacent cutting inserts within a groove coinciding in phase such that the rotational trajectory of said each groove forms a continuous wave. 
 
     
     
       11. The indexable rotary cutting tool according to  claim 10 , wherein:
 when rotational trajectories of all the grooves are superimposed, the rotational trajectories of any two grooves do not coincide with each other in phase. 
 
     
     
       12. The indexable rotary cutting tool according to  claim 9 , wherein:
 the minor cutting edge is connected to a major cutting edge belonging to an adjacent set of cutting edges; 
 lands are formed in the major cutting edge the minor cutting edge, and the corner cutting edge; 
 a land width at a connecting point between the minor cutting edge and the major cutting edge belonging to the adjacent set of cutting edges, is larger than a land width at a center point of the major cutting edge; and 
 a land angle at the connecting point is smaller than a land angle at the center point of the major cutting edge. 
 
     
     
       13. The indexable rotary cutting tool according to  claim 12 , wherein a land width and a land angle of the minor cutting edge are equal to the land width and the land angle at the connecting point. 
     
     
       14. The indexable rotary cutting tool according to  claim 9 , wherein:
 the cutting inserts are mounted such that, during cutting operations when the cutting tool is moved in a lateral direction perpendicular to the rotational axis, an outwardly-curved cutting edge portion belonging to an adjacent set of cutting edges and connected to a minor cutting edge belonging to the operative set of cutting edges, does not participate in cutting.